The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, it relates to a semiconductor device capable of having a wafer of reduced thickness by virtue of reinforcement and a method of manufacturing such a semiconductor device.
A semiconductor device typically uses a wafer of silicon or other material, and various elements, interconnections, electrodes, and the like are integrally formed thereon through a wafer process. Especially, it is known in the art that a device such as an IGBT (Insulated Gate Bipolar Transistor) dedicated to a switching device exhibits enhanced device performance, including a reduced turn-on voltage and a decreased switching loss, by reducing a thickness of its substrate.
Because of this teaching, wafers conventionally used in semiconductor devices have a thickness of 110 to 120 micrometers. But recently, even thinner wafers having a thickness of 100 micrometers or thinner have begun to be used.                With such semiconductor wafers of reduced thickness, however, semiconductor devices, while undergoing an ordinary semiconductor manufacturing process, may become defective, with cracks or chippings in the wafer due to its insufficient strength, which eventually reduces yields of the device products.        
In another approach, the wafer process is performed with a relatively thick wafer and the wafer has its back surface ground and thinned immediately before the dicing. However, the thinned wafer may sometimes be warped due to stress which is generated through different coefficients of thermal expansion between the wafer and a passivation film formed at the final stage of a wafer process.
For grinding the back surface of the wafer, various approaches have been proposed as in Patent Document 1 (Japanese Patent Laid-open No. Hei9-64049(1997)) which discloses a resin reinforcing layer applied on the wafer surface, and as in Patent Document 2 (Japanese Patent Laid-open 2002-100589) which discloses surface protection adhesive tape applied on the wafer surface. Also, in order to avoid the cracking and chipping, manufacturing machines have been frequently improved to attain delicate handling of the wafer.
Such improvements of the manufacturing machine, however, lead to a cost increase in the machines and a degraded workability, and ultimately to a cost increase in the products.